The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to deposit, etch or otherwise treat film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device such as a showerhead and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and heat or radio frequency (RF) plasma may be used during some processes to activate chemical reactions.
The processing chamber typically includes upper and lower surfaces and side walls. The showerhead typically includes a cylindrical base portion defining a gas plenum. A faceplate is arranged on one side of the gas plenum and includes a plurality of spaced through holes. The showerhead further includes a hollow stem portion that is connected at one end to an upper surface of the processing chamber and at an opposite end to a center of the cylindrical base. The stem portion of the showerhead delivers process gas to the gas plenum of the cylindrical base. The gas flows through the spaced through holes of the faceplate and is uniformly dispersed relative to a substrate arranged on a substrate support located below the showerhead.
A collar located around the stem portion may be used to deliver curtain gas to isolate adjacent processing stations with chandelier style showerheads. The collar may also be used to connect the stem portion to the upper surface of the processing chamber. The collar may include one or more gas slits that deliver secondary purge gas between the cylindrical base portion and the upper surface of the processing chamber during processing. A gap is defined between radially outer edges of the cylindrical base portion of the showerhead and the sidewalls of the processing chamber. Secondary purge gas flows through the slits on the collar and the gap and is then evacuated via an exhaust port. The symmetric configuration of the showerhead may cause recirculation of the secondary purge gas. Particles may be trapped by the recirculating gas above the showerhead during processing and may cause defects.